使用偏振观测可视化不可见
Visualizing the Invisible using Polarisation Observations
摘要：
一个电磁波可以用四个斯托克斯参数来唯一地表征：I、Q、U和V。然而，大量关于发射区域和传播路径的信息被携带在剩余的斯托克斯参数中。这些数据提供了一种手段，以观察部分星际介质仍然不可见的斯托克斯I，在任何波长。例如，当一个电磁波传播通过一个包含自由电子和磁场的区域时，波的偏振面将旋转--这种效应只在斯托克斯Q和U中记录。银河系的星际介质就是这样一个区域，包含自由电子（观测为HII）和几微高斯的磁场。通过在斯托克斯Q和U中成像，我们能够观察从小尺度（几十pc）到大尺度（kpc）的磁场扰动的特征。本文综述了加拿大宇宙磁场极化研究的现状，并讨论了加拿大在世界极化研究中的主导作用。
英文摘要：
An electromagnetic wave can be uniquely characterized by the four Stokes parameters: I, Q, U, and V. Typical observations in astronomy rely solely on total intensity measurements of the incoming radiation (Stokes I). However, a significant amount of information both about the emitting region and the propagation path is carried in the remaining Stokes parameters. These data provide a means to observe parts of the interstellar medium which remain invisible in Stokes I, at any wavelength. For example, when an electromagnetic wave propagates through a region containing free electrons and a magnetic field, the plane of polarisation of the wave will rotate - an effect recorded only in Stokes Q and U. The interstellar medium of the Galaxy is such a region, containing free electrons (observed as HII) and a magnetic field of a few microgauss. By imaging in Stokes Q and U we are able to observe signatures of magnetic field perturbations from the small scale (tens of pc) to the large scale (kpc). In this paper, we review the status of Canadian polarisation studies of cosmic magnetic fields and discuss the leading role Canada is playing in polarsation studies around the world.
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